''Texella reddelli'', the Bee Creek cave harvestman, is a rare species of

troglobitic A troglobite (or, formally, troglobiont) is an animal species, or population of a species, strictly bound to underground habitats, such as caves. These are separate from species that mainly live in above-ground habitats but are also able to live u ...

harvestman The Opiliones (formerly Phalangida) are an order of arachnids, colloquially known as harvestmen, harvesters, harvest spiders, or daddy longlegs (see below). , over 6,650 species of harvestmen have been discovered worldwide, although the total n ...

that was added to the United States

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...

list in 1988, at the same time as six other species native to the

karst Karst () is a topography formed from the dissolution of soluble carbonate rocks such as limestone and Dolomite (rock), dolomite. It is characterized by features like poljes above and drainage systems with sinkholes and caves underground. Ther ...

ecosystem in Travis County and Williamson County,

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

, USA. They inhabit areas with near 100% humidity and constant temperatures, and they prey on

springtail Springtails (class Collembola) form the largest of the three lineages of modern Hexapoda, hexapods that are no longer considered insects. Although the three lineages are sometimes grouped together in a class called Entognatha because they have in ...

s. Research on these creatures has been difficult since they can only be found underground. Their distribution is limited and unknown reproductive rates mean that it is possible they are especially susceptible to

habitat destruction Habitat destruction (also termed habitat loss or habitat reduction) occurs when a natural habitat is no longer able to support its native species. The organisms once living there have either moved elsewhere, or are dead, leading to a decrease ...

and other threats. ''Texella reddelli'' are found on both the North and South sides of the

Colorado River The Colorado River () is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and in northern Mexico. The river, the List of longest rivers of the United States (by main stem), 5th longest in the United St ...

Description

These

arachnid Arachnids are arthropods in the Class (biology), class Arachnida () of the subphylum Chelicerata. Arachnida includes, among others, spiders, scorpions, ticks, mites, pseudoscorpions, opiliones, harvestmen, Solifugae, camel spiders, Amblypygi, wh ...

s are about 1/8 of an inch (3.175 mm) long with a yellow-brown color and long legs. Juveniles have a yellowish-white body. They live underground, and have small eyes, and elongated appendages. All seven species live in the Karst

ecosystem An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...

Travis Travis may refer to: People and fictional characters *Travis (given name), a list of people and fictional characters *Travis (surname), a list of people Places in the United States *Travis, Staten Island, a neighborhood *Travis Air Force Base, a ...

and Williamson counties in Texas.

Habitat

Bee Creek cave harvestman inhabit

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

caves. They are only able to survive in caves that maintain stable temperatures and humidity (close to 100%). They have been found in caves both on the north and south side of the Colorado river. They live in the karst terrain in Travis County, which is formed by "dissolution of

calcium carbonate Calcium carbonate is a chemical compound with the chemical formula . It is a common substance found in Rock (geology), rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skel ...

from limestone bedrock by mildly acidic

groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit ...

." This process creates the caves that are needed to support this species. They receive their nutrients through groundwater infiltration.

Troglobites

''Texella reddelli'' is a type of

troglobite A troglobite (or, formally, troglobiont) is an animal species, or population of a species, strictly bound to underground habitats, such as caves. These are separate from species that mainly live in above-ground habitats but are also able to live u ...

. These species survived in the cave environment and adapted to it. The Karst terrain created caves that were not always connected with each other. This brought about "islands" of individual populations that were disconnected for long periods of time. Over time the separate groups became different species because of the isolation. The rate at which each population speciated was different. The species that are more mobile have larger ranges and are less isolated. Since they are all still relatively close together, disturbances can make them highly susceptible to

extinction Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

. They require stable temperatures and often stay in remote corners or the ceiling of the cave that are the warmest.

Location

Since 1988 when these species were first listed as endangered, other caves containing these species have been discovered, along with new

endemic species Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

. Due to the intensive requirements to find caves, much of the karst area has not been searched. To date, over 700 karst features have been located in two counties in Texas, while only 100 of these are believed to contain endangered species. While the number of locations in which these endangered species are found may increase, the total range of each species is not expected to grow. '' Texella reyesi'' was considered ''T. reddelli'' because of their similarities, but it has since been identified as different and now is also on the endangered species list. ''Texella reddelli'' is known from only three caves in the Jollyville

plateau In geology and physical geography, a plateau (; ; : plateaus or plateaux), also called a high plain or a tableland, is an area of a highland consisting of flat terrain that is raised sharply above the surrounding area on at least one side. ...

and four caves in the Rollingwood region. Those that were originally thought to be ''T. reddelli'', but now are renamed ''Texella reyesi'' occur in Tooth, McDonald, Weldon, and Root caves, also in Texas.

Karst

The

ecosystem in Texas is provided water by surface drainage and groundwater. The water travels rapidly through cave openings and fractures. This provides very little or no purification, which can leave the cave susceptible to pollution from contaminated water. This is a problem in certain areas where runoff can be a problem or in agricultural areas where herbicides and pesticides are used. Contaminants are one of the main threats to these species, along with urban development. In a karst ecosystem the surface communities are very important for

photosynthesis Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...

. These plant and animal communities are essential for nutrients and energy. Nutrients travel from the surface in the form of organic debris. The surface plant communities around this ecosystem can range from pasture land to woodlands. Exotic plants and animals are detrimental to native species because they compete for food and decrease overall species diversity. The surface community also serves as a buffer against temperature and moisture change and can filter out some pollutants.

Threats

The area in which the species occur is going through urban expansion at a rapid rate. Very few of the caves are capable of handling a change and many of the caves already occur close to developed areas, such as roads, schools, houses, golf courses, and commercial centers. Changes in drainage patterns along with increases in pollution could cause a collapse of caves. Although some caves have already been filled or collapsed, it is hard to estimate how many have already been lost. Elliott and Reddell (1989) estimate that 10% of caves in Travis County are destroyed every 10 years.

Development Development or developing may refer to: Arts *Development (music), the process by which thematic material is reshaped * Photographic development *Filmmaking, development phase, including finance and budgeting * Development hell, when a proje ...

activities that result in the alteration of natural drainage patterns can negatively affect these species. This can include altering the

topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the landforms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary sci ...

, increasing or decreasing cover,

irrigation Irrigation (also referred to as watering of plants) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has bee ...

systems, and other activities. Fire

ants Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of ...

are especially detrimental to the Karst ecosystem, although the main threat to the species is loss of habitat to urban development. The fire ant is an aggressive predator and it has devastating and long lasting impacts on native ant and arthropod communities. The shallow caves makes ''Texella reddelli'' vulnerable to invasion by fire ants and other exotic species. Fire ants have been found in over 50% of the caves that are known to contain endangered species in this ecosystem. Even if the fire ants do not always directly prey upon the ''Texella reddelli'', their presence can have a negative effect on the ecosystem and species that are critical in the

food chain A food chain is a linear network of links in a food web, often starting with an autotroph (such as grass or algae), also called a producer, and typically ending at an apex predator (such as grizzly bears or killer whales), detritivore (such as ...

Recovery

The future of these several species depends on the protection of key areas of the Karst ecosystem. Areas that are chosen should not be close together in case of a disaster and in order to protect the maximum

genetic diversity Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species. It ranges widely, from the number of species to differences within species, and can be correlated to the span of survival for a species. It is d ...

. The troglobites require protection from contaminated ground water and other non-native predators such as fire ants.

References

{{Taxonbar, from=Q2555267 Harvestmen Cave arachnids Animals described in 1967 Arthropods of the United States Endemic fauna of Texas Taxobox binomials not recognized by IUCN